Memory provides data storage for electronic systems. Flash memory is one of various memory types, which has numerous uses in modern computers and devices. A typical flash memory may comprise a memory array that includes a large number of non-volatile memory cells arranged in row and column fashion. The cells may usually be grouped into blocks. Each of the cells within a block may be electrically programmed by charging a floating gate associated with the cell. Data may be stored in a cell as charge in the floating gate. The data may be erased by a block erase operation that removes the charges in the floating gates of cells of a block.
In recent years, vertical memory, such as three-dimensional (3D) memory has been developed. A 3D flash memory (e.g., 3D NAND memory array) device may include a plurality of strings of memory cells stacked over one another, with each memory cell of a string corresponding to one of multiple tiers of the device. The memory cells of a respective string may share a common channel region, such as one formed as a respective pillar of semiconductor material (e.g., polysilicon) about which the string of memory cells may be formed.
In another dimension of the 3D flash memory device, a group of strings may share a plurality of access lines, known as wordlines (WLs). Each of the plurality of wordlines may be coupled (e.g., electrically or otherwise operably connected) with respective memory cells of each string in the group of strings.
In a third dimension of the 3D flash memory device, groups of strings may be coupled to respective data lines of a set of data lines, known as bitlines (BLs). A 3D memory may be divided into memory blocks, comprising a plurality of memory pages, selectable via drain-side select gate (hereinafter select gate drain (SGD)) devices and source-side select gate (select gate source (SGS)) devices that may be provided over each end of the pillars to control memory cells. A 3D NAND memory array may utilize floating body pillars with SGS and SGD at the edge. A block of memory cells may correspond to a smallest group of memory cells that can be erased by a block erase operation (e.g., it is not possible to erase some memory cells of a block while maintaining the data in other memory cells of the block).